Pen, sensor device, and pen system

ABSTRACT

A pen is configured to supply an N-bit internal digital value NA to a sensor device, and includes an integrated circuit that acquires a series of the internal digital values NA(s) based on a state OPS of a writing pressure detector. The integrated circuit supplies a first internal digital value NA to the sensor device by transmitting, from an antenna, first transmission data MF including a first standard digital value MS corresponding to the first internal digital value NA. The integrated circuit supplies a second internal digital value NA to the sensor device by transmitting, from the antenna, second transmission data MF that is smaller than N bits and includes an M-bit relative digital value (M&lt;N) corresponding to a relative value between the first internal digital value NA obtained by restoration from the first standard digital value MS and the second internal digital value NA.

BACKGROUND Technical Field

The present disclosure relates to a pen, a sensor device, and a pensystem, and particularly relates to a pen that transmits a digitalvalue, a sensor device that receives the digital value, and a pen systemincluding the pen and the sensor device.

Description of the Related Art

A pen that transmits a digital value toward a sensor device by changingan alternating current (AC) electric field, AC magnetic field, or ACelectromagnetic field is known. For example, in Patent Document 1, a penthat transmits a digital value, which represents information oncontinuous quantity (for example, a writing pressure) corresponding to acontinuous operation, toward a sensor device is disclosed.

Furthermore, a display device is known, in which a touch sensorconfiguring a sensor device is incorporated based on an in-cell system.In a pen system using this kind of display device, signal transmissionfrom a pen to the sensor device is carried out in a display'snon-driving period. However, the time length of the display'snon-driving period may be too short to transmit a writing pressurevalue, which is fixed-length data. Thus, the transmission of the writingpressure value may need to be executed in such a manner as to be dividedin plural display's non-driving periods, which exist in a dispersedmanner in one frame defined by an uplink signal. In Patent Document 2, apen system that carries out such divided transmission is disclosed.

PRIOR ART DOCUMENT Patent Documents

Patent Document 1: Japanese Patent No. 3135183

Patent Document 2: International Publication Pamphlet No. WO 2018/066100

BRIEF SUMMARY Technical Problem

In recent years, the size of data transmitted from the pen toward thesensor device has been increasing: a writing pressure value is expressedwith 8196 grayscale levels, for example. As a result, particularly in asystem in which the communication time is limited within the display'snon-driving period as in Patent Document 2, or the like, communicationresources that can be used for communication between the pen and thesensor device tend to be insufficient and improvement is needed. Inaddition, in recent years, the multi-pen system that allows simultaneoususe of plural pens has been widespread and communication resources arebecoming scarce.

According to one aspect of the present disclosure, a pen, a sensordevice, and a pen system are provided that can alleviate insufficiencyof communication resources used for communication between a pen and asensor device.

Technical Solution

A pen according to a first aspect of the present disclosure is a penthat supplies an N-bit internal digital value to a sensor device. Thepen includes a writing pressure detector that detects a force applied toa pen tip, an antenna, and an integrated circuit that is connected tothe writing pressure detector and the antenna and that acquires a seriesof the internal digital values based on a state of the writing pressuredetector. The series of the internal digital values includes a firstinternal digital value and a second internal digital value acquiredsubsequently to the first internal digital value. The integrated circuitsupplies the first internal digital value to the sensor device bytransmitting, from the antenna, first transmission data including afirst standard digital value corresponding to the first internal digitalvalue. The integrated circuit supplies the second internal digital valueto the sensor device by transmitting, from the antenna, secondtransmission data that is smaller than N bits and includes an M-bitrelative digital value (M<N) corresponding to a relative value betweenthe first internal digital value, which can be restored from the firststandard digital value, and the second internal digital value.

A sensor device according to the first aspect of the present disclosureis a sensor device that receives supply of a series of internal digitalvalues each composed of N bits from a pen configured to acquire theseries of internal digital values based on a force applied to a pen tip.The series of internal digital values include a first internal digitalvalue and a second internal digital value acquired subsequently to thefirst internal digital value. When receiving first transmission dataincluding a first standard digital value corresponding to the firstinternal digital value from the pen, the sensor device restores thefirst internal digital value from the first transmission data and storesthe first internal digital value in an internal memory. When receiving,from the pen, second transmission data that is smaller than N bits andincludes an M-bit relative digital value (M<N) corresponding to arelative value between the first internal digital value, which isrestored from the first standard digital value, and the second internaldigital value, the sensor device restores the second internal digitalvalue from the second transmission data by using the value stored in theinternal memory.

A pen according to a second aspect of the present disclosure is a penthat supplies an N-bit internal digital value to a sensor device. Thepen includes an antenna and an integrated circuit that is connected to auser operation tool and the antenna and that acquires a series of theinternal digital values. The integrated circuit receives a referencevalue corresponding to the internal digital value that has been alreadysupplied from the sensor device and supplies a first internal digitalvalue included in the series of the internal digital values to thesensor device by transmitting, from the antenna, transmission data thatis smaller than N bits and includes an M-bit relative digital value(M<N) corresponding to a relative value between the first internaldigital value and the reference value.

A sensor device according to the second aspect of the present disclosureis a sensor device that receives supply of a series of internal digitalvalues each composed of N bits from a pen configured to acquire theseries of internal digital values based on a force applied to a pen tip.The sensor device transmits a reference value to the pen. Whenreceiving, from the pen, transmission data that is smaller than N bitsand includes an M-bit relative digital value (M<N) corresponding to arelative value between a first internal digital value included in theseries of internal digital values and the reference value, the sensordevice restores the first internal digital value from the transmissiondata by using the reference value.

A pen system according to the present disclosure is a pen system thatincludes a pen and a device and that outputs an N-bit internal digitalvalue. The pen includes a writing pressure detector that detects a forceapplied to a pen tip, an antenna, and an integrated circuit that isconnected to the writing pressure detector and the antenna and thatacquires a series of the internal digital values based on a state of thewriting pressure detector. The integrated circuit supplies a firstinternal digital value included in the series of the internal digitalvalues to the sensor device by transmitting, from the antenna, firsttransmission data including a standard digital value. The referencedigital value is obtained by compressing the first internal digitalvalue using a compression method, in which a quantization step becomessmaller when a value of the internal digital value is smaller. Thedevice is configured to restore the first internal digital value fromthe first transmission data and to output the first internal digitalvalue.

Advantageous Effect

According to the first aspect of the present disclosure, the N-bitinternal digital value can be supplied using the transmission data thatis smaller than N bits. Thus, it becomes possible to alleviateinsufficiency of communication resources that can be used forcommunication between the pen and the sensor device.

According to the second aspect of the present disclosure, even when adiscrepancy occurs between the internal digital value acquired by thepen and the internal digital value acquired by the sensor device due toa communication error or the like, the error can be eliminated once thereference value is transmitted and received.

According to the pen system in accordance with the present disclosure,it becomes possible to reduce the possibility that the user senses anerror that possibly occurs at the time of transmission of the standarddigital value.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the system configuration of a pensystem according to a first embodiment of the present disclosure.

FIG. 2 is a diagram explaining the principle of the first embodiment ofthe present disclosure.

FIG. 3 is a schematic block diagram illustrating functional blocks of anintegrated circuit.

FIG. 4 is a flowchart illustrating a transmission processing of aninternal digital value NA executed by the integrated circuit.

FIGS. 5A and 5B are each a diagram illustrating one example of acompression method of the internal digital value NA.

FIG. 6 is a diagram illustrating a specific example of the respectivevalues used in the process of the processing illustrated in FIG. 4 .

FIG. 7 is a diagram illustrating a specific example of the respectivevalues used in the process of the processing illustrated in FIG. 4 .

FIG. 8 is a flowchart illustrating a reception processing of theinternal digital value NA executed by a sensor controller.

FIGS. 9A and 9B are each a diagram illustrating a temporal change invarious digital values acquired in each of a pen and a sensor device.

FIG. 10 is a diagram illustrating a working example of the firstembodiment of the present disclosure.

FIG. 11 is a diagram illustrating a working example of the firstembodiment of the present disclosure.

FIG. 12 is a diagram illustrating the working example of the firstembodiment of the present disclosure.

FIG. 13 is a diagram illustrating the working example of the firstembodiment of the present disclosure.

FIG. 14 is a diagram explaining the principle of a second embodiment ofthe present disclosure.

FIG. 15 is a flowchart illustrating a transmission processing of theinternal digital value NA executed by the integrated circuit accordingto the second embodiment of the present disclosure.

FIG. 16 is a flowchart illustrating a reception processing of theinternal digital value NA executed by the sensor controller according tothe second embodiment of the present disclosure.

FIG. 17 is a diagram illustrating a working example of the secondembodiment of the present disclosure.

FIG. 18 is a flowchart illustrating a transmission processing of theinternal digital value NA executed by the integrated circuit accordingto a third embodiment of the present disclosure.

FIG. 19 is a flowchart illustrating a reception processing of theinternal digital value NA executed by the sensor controller according tothe third embodiment of the present disclosure.

FIG. 20 is a diagram illustrating a working example of the thirdembodiment of the present disclosure.

FIG. 21 is a diagram illustrating a temporal change in various digitalvalues acquired in each of the pen and the sensor device according to afourth embodiment of the present disclosure.

FIG. 22 is a schematic block diagram illustrating functional blocks ofthe integrated circuit according to the fourth embodiment of the presentdisclosure.

FIG. 23 is a flowchart illustrating a processing executed by theintegrated circuit according to a fifth embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described in detail belowwith reference to the accompanying drawings.

FIG. 1 is a diagram illustrating the system configuration of a pensystem 1 according to a first embodiment of the present disclosure. Asillustrated in this diagram, the pen system 1 according to the presentembodiment is configured to have a pen 2, a sensor device 3, and a hostcomputer 4. Among them, the host computer 4 may be any of various typesof computer such as a tablet type computer, a notebook type computer,and a desktop type computer.

The sensor device 3 is a position detecting device compatible withvarious systems such as active electrostatic (ES) system,electromagnetic resonance (EMR) system, pressure sensing system, and isconfigured to have a sensor 30, which forms a touch surface 3 t, and asensor controller 31 that is an integrated circuit. Althoughdiagrammatic representation is not made, the sensor 30 has aconfiguration in which plural electrodes are disposed in the touchsurface 3 t. The sensor controller 31 detects the position of the pen 2in the touch surface 3 t by using these electrodes. In addition, thesensor controller 31 receives, through these electrodes, datatransmitted from the pen 2 by receiving a signal transmitted from thepen 2 (hereinafter referred to as a “downlink signal DS”).

The case in which the sensor device 3 is compatible with the active ESsystem or electromagnetic resonance (EMR) system will be specificallydescribed. In the downlink signal DS, an unmodulated burst signal and adata signal obtained by modulation with various kinds of data areincluded. The burst signal is a signal used for detection of theposition of the pen 2 in (on) the touch surface 3 t by the sensorcontroller 31. The sensor controller 31 determines the electrode bywhich the burst signal has been received by sequentially scanning theplural electrodes configuring the sensor 30, and detects the position ofthe pen 2 based on the result thereof. The data signal is a signalincluding various internal digital values acquired by the pen 2 (awriting pressure value, a wheel indication value, and so forth acquiredby a user operation tool 25 to be described later). The sensorcontroller 31 receives data transmitted from the pen 2 by using theelectrode, which is closest to the position of the pen 2 in the pluralelectrodes forming the sensor 30, as an antenna and receiving the datasignal.

Signal transmission from the sensor controller 31 to the pen 2 may alsobe allowed. Hereinafter, the signal thus transmitted will be referred toas “uplink signal US.” The sensor controller 31 uses the pluralelectrodes forming the sensor 30 as the transmitting antenna andtransmits the uplink signal US.

An instruction (or a command) from the sensor controller 31 to the pen 2can be included in the uplink signal US. The pen 2 determines thetransmission timing of the downlink signal DS based on the timing whenthe uplink signal US is received. In addition, the pen 2 determines thekind of internal digital value transmitted in the downlink signal DSbased on the command included in the uplink signal US.

The sensor controller 31 supplies the detected position and the receiveddata to the host computer 4. The host computer 4 generates and storesstroke data indicating the trace formed by the pen 2 based on the seriesof positions and signals thus supplied, and carries out rendering of thestored stroke data.

In the present embodiment, a description will be made based on theassumption that the uplink signal US and the downlink signal DS aretransmitted and received through the sensor 30. However, the uplinksignal US may be transmitted and received by another communicationsystem (for example, Bluetooth (registered trademark), wireless LAN, orthe like).

In one example, the sensor 30 is incorporated in a display device of thehost computer 4, which may be a tablet type computer based on thein-cell system. In this case, in order to avoid the influence of noisegenerated due to pixel driving carried out in the display device,transmission and reception of the uplink signal US and the downlinksignal DS may be carried out during the display's non-driving periodsuch as the vertical blanking period or horizontal blanking period of aliquid crystal display device, for example. Because the transmission andreception of the uplink signal US and the downlink signal DS are notcarried out during the display's driving period, communication resourcesthat can be used for communication between the pen 2 and the sensordevice 3 are significantly limited.

Here, between the pen 2 and the sensor device 3 having the sensor 30incorporated in the display device based on the in-cell system, normallycommunication is carried out based on frame communication in whichplural time slots (=the display's non-driving periods) are included inone frame. In this case, the time slot used for transmission of theuplink signal US is configured separately from the time slot used fortransmission of the downlink signal DS, in advance. Therefore, even whena reference value Ref is transmitted by the uplink signal US asdescribed in a fourth embodiment, such uplink transmission does notinterfere with the transmission of the downlink signal DS.

The pen 2 is an electronic pen compatible with the same system as thesensor device 3 (for example, active electrostatic (ES) system orelectromagnetic resonance (EMR) system) and is configured to have a corebody 20, an antenna 22, a writing pressure detector 23, a power supply26, and an integrated circuit 27.

The core body 20 is a bar-shaped member disposed in such a manner thatits longitudinal direction corresponds with the pan axis direction ofthe pen 2, and its one end forms a pen tip 21 of the pen 2. Anelectrically-conductive material is applied to the surface of the corebody 20, which forms the antenna 22.

The antenna 22 is an electrical conductor disposed near the core body 20and is electrically connected to the integrated circuit 27 by a wiringline. The integrated circuit 27 carries out reception of theabove-described uplink signal US and transmission of the downlink signalDS through this antenna 22. Signals other than the above-described burstsignal may be transmitted and received by using an antenna other thanthe antenna 22 (not illustrated, for example, a built-in antenna forBluetooth (registered trademark)). Furthermore, the antenna 22 may beseparated into an antenna for transmission and an antenna for reception.

The writing pressure detector 23 is a functional unit that detects aforce (a writing pressure) applied to the pen tip 21. Specifically, thewriting pressure detector 23 abuts against the rear end part of the corebody 20 and is configured to detect, through this abutting, the forceapplied to the pen tip 21 when the user presses the pen tip of the pen 2against the touch surface 3 t or the like. In a specific example, thewriting pressure detector 23 is formed of a variable-capacitance modulewhose capacitance changes according to the force applied to the pen tip21.

Here, it can be said that the writing pressure detector 23 is a useroperation tool that detects the amount of operation by the user(specifically, a magnitude of the force with which the user presses thetouch surface 3 t), and the pen 2 can include such user operation tool25 besides the writing pressure detector 23. For example, the pen 2 mayinclude a wheel that can be rotated by the user, or a wheel operationtool that detects the amount of rotation of the wheel.

The power supply 26 is a component for supplying operating power(direct-current voltage) to the integrated circuit 27 and is formed ofan AAAA battery with a cylindrical shape, for example.

The integrated circuit 27 is a processing unit formed of a circuit groupformed on a board that is not illustrated, and is connected to the useroperation tool 25 and the antenna 22. If an antenna other than theantenna 22 is used for reception of the uplink signal US or transmissionof the downlink signal DS, the integrated circuit 27 is connected alsoto such antenna. The integrated circuit 27 is responsible for acquiringa series of internal digital values NA(s) each composed of N bits basedon a state of the writing pressure detector 23 (or a state of anotheruser operation tool) and sequentially supplying the internal digitalvalues NA(s) to the sensor device 3 by using the downlink signal DS.However, when the internal digital values NA(s) are transmitted usingthe number of bits N as is, there is a possibility that communicationresources may become insufficient. Thus, as illustrated in FIG. 1 , aconfiguration is made such that the internal digital values NA(s) aretransmitted after being converted to transmission data MF that issmaller than N bits. A characteristic of the present embodiment is thatthe pen 2 and the sensor device 3 are configured in such a manner that,although the integrated circuit 27 transmits the transmission data MFsmaller than N bits, the original N-bit internal digital value NA can berestored in the sensor device 3 and the N-bit internal digital value NAcan be provided to the host computer 4. This point will be described indetail below.

First, FIG. 2 is a diagram explaining the principle of the presentembodiment. The integrated circuit 27 is configured to, in transmittingthe N-bit internal digital value NA, transmit the transmission data MFof M+1 bits, instead of the internal digital value NA itself. Thetransmission data MR includes an M-bit (M<N−1) transmission digitalvalue MD, which is either of a standard digital value MS or a relativedigital value MR as illustrated in FIG. 2 , and a one-bit identificationflag F indicating the kind of transmission digital value MD.

The standard digital value MS is a value corresponding to the internaldigital value NA and, specifically, is formed of an M-bit digital valueobtained by compressing the internal digital value NA. This compressionis carried out by discarding the least significant N−M bits of theinternal digital value NA in the example of FIG. 2 . However, it is alsopossible to obtain the standard digital value MS by another compressionmethod as described later.

The relative digital value MR is an M-bit digital value corresponding tothe relative value between the internal digital value NA, which is beingsupplied, and the internal digital value NA, which has been alreadysupplied to the sensor device 3. The internal digital value NA that hasbeen already supplied means the internal digital value NA restored fromthe transmission digital value MD that has been actually transmitted,and is the same as the internal digital value NA restored by the sensordevice 3 that has received this transmission digital value MD (as longas a communication error to be described later does not exist). Therelative value may be the difference between the internal digital valueNA , which is being supplied, and the internal digital value NA that hasbeen already supplied to the sensor device 3, for example.

As described in detail later, the integrated circuit 27 is configured toset the standard digital value MS as the transmission digital value MD,in a case where communication has just started and so the internaldigital value NA has not been supplied yet, or in a case where theinternal digital value NA is what can be restored from the standarddigital value MS without an error (for example, in a case where the N−Mleast significant bits of the internal digital value NA are all 0), orin a case where the relative value cannot be expressed with M bits. Theintegrated circuit 27 is configured to set the relative digital value MRas the transmission digital value MD, in a case where the internaldigital value NA that has been already supplied exists and the internaldigital value NA is not what can be restored from the standard digitalvalue MS without an error (for example, the N−M least significant bitsof the internal digital value NA include a bit that is not 0) and therelative value can be expressed with M bits. The case in which therelative value cannot be expressed with M bits corresponds to the casein which the relative value is not in a range of −2^(M−1)+2^(M−1)−1, forexample, where a negative digital value is expressed by using a two'scomplement.

When receiving the transmission data MF smaller than N bits from the pen2, first, the sensor controller 31 determines which of the standarddigital value MS or the relative digital value MR is included in thetransmission data MF based on the identification flag F. If it isdetermined that the transmission data MF includes the standard digitalvalue MS, the internal digital value NA is restored from thetransmission digital value MD (=the standard digital value MS) and therestored internal digital value NA is stored in an internal memory,which is not illustrated. In the example of FIG. 2 , this restoration iscarried out by complementing the N−M least significant bits with apredetermined value (for example, 0). In this case, an errorcorresponding to up to N−M bits possibly occurs.

On the other hand, when determining that the transmission data MFincludes the relative digital value MR, the sensor controller 31 isconfigured to restore the internal digital value NA from thetransmission digital value MD (=the relative digital value MR) by usingthe value stored in the internal memory and to store the restoredinternal digital value NA in the internal memory. If the relativedigital value MR is composed of the difference between the internaldigital value NA being supplied and the internal digital value NA thathas been already supplied to the sensor device 3 as in theabove-described example, this restoration is carried out by adding thevalue stored in the internal memory and the received relative digitalvalue MR. The internal digital value NA restored from the relativedigital value MR is data that does not include an error and maintains anaccuracy of N bits, as long as the transmission data MF is not lost dueto a communication error or the like.

As above, according to the present embodiment, the N-bit internaldigital value NA can be supplied with the transmission data MF smallerthan N bits (specifically, with M+1 bits). Furthermore, although acertain level of error possibly occurs when the standard digital valueMS is transmitted, this error can be eliminated by the relative digitalvalue MR which immediately follows and, therefore, does not become asubstantial problem. In addition, an error attributed to transmission ofthe standard digital value MS occurs when the relative value is large,i.e., when a change in the internal digital value NA is large. In such acase, even when a certain degree of error exists, the impact on theperception of a human user is limited (as compared with the case inwhich a change in the internal digital value NA is small). Therefore,according to the present embodiment, it becomes possible to alleviateinsufficiency (or shortage) of communication resources that can be usedfor communication between the pen 2 and the sensor device 3. A specificconfiguration to supply such internal digital value NA will be describedin detail below.

FIG. 3 is a schematic block diagram illustrating functional blocks ofthe integrated circuit 27. As illustrated in FIG. 3 , the integratedcircuit 27 is configured to functionally include an internal digitalvalue acquisition circuit 100, a transmission digital value acquisitioncircuit 101, a transmission circuit 102, and an already-suppliedinternal digital value holding circuit 103.

The internal digital value acquisition circuit 100 is a functional unitthat sequentially converts a state OPS of the writing pressure detector23 (or a state of another user operation tool 25) to the N-bit internaldigital value. The internal digital value acquisition circuit 100sequentially supplies a series of internal digital values NA(s) acquiredby the conversion to the transmission digital value acquisition circuit101.

The transmission digital value acquisition circuit 101 is a functionalunit that generates the transmission data MF including the transmissiondigital value MD and the identification flag F based on the internaldigital value NA supplied from the internal digital value acquisitioncircuit 100 and supplies the transmission data MF to the transmissioncircuit 102. The transmission digital value acquisition circuit 101, inresponse to the internal digital value NA that is newly supplied,determines which of the standard digital value MS or the relativedigital value MR is to be set as the next transmission digital value MDto be transmitted based on the internal digital value NA, and generatesthe transmission data MF including either of the standard digital valueMS or the relative digital value MR based on the determination result.

This determination is composed of two determinations. The firstdetermination is a determination of whether or not the internal digitalvalue NA is what can be restored from the standard digital value MSwithout an error. The transmission digital value acquisition circuit101, which has determined that the internal digital value NA can berestored without an error, acquires the standard digital value MScorresponding to the internal digital value NA and sets the referencedigital value MS as the transmission digital value MD to be transmittednext.

The second determination is a determination of whether or not therelative value between an already-supplied internal digital value NSheld in the already-supplied internal digital value holding circuit 103and the internal digital value NA being supplied can be expressed with Mbits, and is carried out in response to determining that the internaldigital value NA cannot be restored without an error in the firstdetermination. When determining that the relative value cannot beexpressed with M bits, the transmission digital value acquisitioncircuit 101 acquires the standard digital value MS corresponding to theinternal digital value NA and sets the reference digital value MS as thetransmission digital value MD to be transmitted next. On the other hand,when determining that the relative value can be expressed with M bits,the transmission digital value acquisition circuit 101 acquires therelative value as the relative digital value MR and sets the relativedigital value MR as the transmission digital value MD to be transmittednext.

The transmission digital value acquisition circuit 101 may further carryout, before the first determination, a determination of whether thealready-supplied internal digital value holding circuit 103 holds avalue (for example, 0 if the internal digital value NA is the writingpressure) indicating that, after the last pen-up (separation of the pentip 21 from the touch surface 3 t), the standard digital value MS hasnever been transmitted. If the result of this determination is positive,the transmission digital value acquisition circuit 101 may set thestandard digital value MS as the transmission digital value MD to betransmitted next irrespective of the above-described two determinations.This makes it possible to prevent the situation in which the relativedigital value MR is transmitted without the standard digital value MSbeing transmitted at the time of pen-down (contact of the pen tip 21with the touch surface 3 t).

The already-supplied internal digital value holding circuit 103 is afunctional unit configured to include one or more N-bit registers and isresponsible for holding the already-supplied internal digital value NS.The specific held content of the already-supplied internal digital valueNS depends on the content of the transmission digital value MD generatedby the transmission digital value acquisition circuit 101. For example,if the transmission digital value acquisition circuit 101 sets thestandard digital value MS as the transmission digital value MD, theinternal digital value NA restored from the standard digital value MS(this internal digital value NA does not necessarily correspond with theinternal digital value NA acquired by the internal digital valueacquisition circuit 100) is set in the already-supplied internal digitalvalue holding circuit 103. On the other hand, if the transmissiondigital value acquisition circuit 101 sets the relative digital value MRas the transmission digital value MD, the internal digital value NArestored from the relative digital value MR by use of thealready-supplied internal digital value NS held in the already-suppliedinternal digital value holding circuit 103 is set in thealready-supplied internal digital value holding circuit 103. In thiscase, the restored internal digital value NA precisely corresponds withthe internal digital value NA acquired by the internal digital valueacquisition circuit 100. Thus, instead of the restored internal digitalvalue NA, the internal digital value NA acquired by the internal digitalvalue acquisition circuit 100 may be set in the already-suppliedinternal digital value holding circuit 103.

The acquisition of the internal digital value NA by the internal digitalvalue acquisition circuit 100 is not always carried out, but carried outonly when the internal digital value NA needs to be supplied to thesensor device 3 (for example, when the pen 2 is detecting the sensordevice 3). The operation of the transmission digital value acquisitioncircuit 101 is carried out in response to supply of the new internaldigital value NA from the internal digital value acquisition circuit100. Therefore, depending on a case, the held content of thealready-supplied internal digital value holding circuit 103 may be notupdated for a long time. Thus, the already-supplied internal digitalvalue holding circuit 103 may be configured to autonomously delete theheld content when the held content is not updated over a predeterminedtime.

The transmission circuit 102 is a functional unit that transmits, to thesensor device 3 through the antenna 22, the transmission data MFsupplied from the transmission digital value acquisition circuit 101 aspart of a data signal which forms the downlink signal DS.

FIG. 4 is a flowchart illustrating a transmission processing of theinternal digital value NA executed by the integrated circuit 27. Withreference to this diagram, the transmission processing of the internaldigital value NA executed by the integrated circuit 27 will be describedmore specifically below.

First, the integrated circuit 27 acquires the N-bit internal digitalvalue NA based on the state OPS (see FIG. 3 ) of the user operation tool25 (step S1). Subsequently, the integrated circuit 27 determines whetheror not the internal digital value NA acquired in step S1 is what can berestored from the standard digital value MS without an error (step S3).This processing may be executed after step S5 to be described later. Asin the example of FIG. 2 , when the standard digital value MS iscomposed of the M most significant bits of the internal digital value NAand the sensor device 3 is configured to restore the internal digitalvalue NA from the standard digital value MS by complementing the N−Mleast significant bits with a predetermined value (for example, 0), theresult of this determination becomes positive if the N−M leastsignificant bits of the internal digital value NA are all 0, and becomesnegative if not so. When determining that the internal digital value NAcan be restored without an error in this determination, the integratedcircuit 27 moves the processing to step S6 irrespective of the relativevalue acquired in step S4 to be described later. When determining thatthe internal digital value NA cannot be restored without an error, theintegrated circuit 27 moves the processing to step S4.

In step S4, the integrated circuit 27 acquires the relative valuebetween the already-supplied internal digital value NS and the internaldigital value NA acquired in step S1 (step S4). The relative valueacquired here is the difference between the already-supplied internaldigital value NS and the internal digital value NA acquired in step S1as described above, for example. Then, the integrated circuit 27determines whether or not the acquired relative value is a numericalvalue that can be expressed with M bits (step S5). When determining thatthe relative value cannot be expressed in this determination, theintegrated circuit 27 moves the processing to step S6. When determiningthat the relative value can be so expressed, the integrated circuit 27moves the processing to step S9.

In step S6, the integrated circuit 27 acquires the M-bit standarddigital value MS by compressing the internal digital value NA (step S6).This compression is processing of extracting the M most significant bitsof the internal digital value NA to make the standard digital value MSas described above, for example.

With reference to FIG. 5 , the compression method of the internaldigital value NA will be described in more detail.

FIGS. 5A and 5B are each a diagram illustrating one example of thecompression method of the internal digital value NA. In these diagrams,examples of N=12 and M=8 are illustrated. Both compression methods areprocessing of converting a discrete value expressed with arelatively-large number of bits (the internal digital value NA) to adiscrete value expressed with a relatively-small number of bits (thestandard digital value MS).

The compression method illustrated in FIG. 5A is a method in which 2^(N)kinds of internal digital values NA(s) that can be expressed with N bitsare separated into total 2^(M) ranges (hereinafter, the size of thisrange will be referred to as “quantization step”) in units of 2^(N−M)values sequentially from the smallest value, and in which the value ofthe standard digital value MS is allocated to each range. Thiscompression method is a processing of extracting the M most significantbits of the internal digital value NA to make the standard digital valueMS. Therefore, when employing the compression method illustrated in FIG.5A, it is preferable that the integrated circuit 27 be configured toacquire the standard digital value MS using the processing of extractingthe M most significant bits of the internal digital value NA.Furthermore, it is preferable for the sensor device 3 that has receivedthe standard digital value MS to restore the internal digital value NAby complementing the N−M least significant bits with a predeterminedvalue (for example, 0) as described above.

The compression method illustrated in FIG. 5B is the same as thecompression method illustrated in FIG. 5A in that 2^(N) kinds ofinternal digital values NA(s) are separated into 2^(M) rangessequentially from the smallest value and the value of the standarddigital value MS is allocated to each range. However, the compressionmethod illustrated in FIG. 5B is different from the compression methodillustrated in FIG. 5A in that the boundaries of the ranges are adjustedin such a manner that the quantization step becomes smaller when thevalue of the internal digital value NA is smaller. In FIG. 5B, theexample is illustrated in which the quantization step when the internaldigital value NA is 0 to 5 is set to 1, and the quantization step whenthe internal digital value NA is 620 to 658 is set to 13, and thequantization step when the internal digital value NA is 2042 to 2133 isset to 23, and the quantization step when the internal digital value NAis 3968 to 4095 is set to 32. Regarding the intermediate internaldigital values NA(s) that are not illustrated in the diagram, it ispreferable to set the quantization step in such a manner that thequantization step rises in a stepwise manner in association with therise of the internal digital value NA.

When employing the compression method illustrated in FIG. 5B, it ispreferable that the integrated circuit 27 be configured to store, inadvance, a table that associates the standard digital value MS with eachinternal digital value NA and to convert the internal digital value NAto the standard digital value MS by referring to this table.Furthermore, regarding the sensor device 3 that has received thestandard digital value MS, it is preferable that the sensor device 3 beconfigured to store, in advance, a table that associates one of theplural values belonging to the corresponding range of the internaldigital value NA (for example, median or maximum value) with eachstandard digital value MS and to restore the internal digital value NAfrom the standard digital value MS by referring to this table.

Using either the compression method of FIG. 5A or the compression methodof FIG. 5B, the N-bit internal digital value NA is compressed to theM-bit standard digital value MS. However, according to the compressionmethod of FIG. 5B, the compression rate of the standard digital value MSwhen the internal digital value NA is small can be made low comparedwith the compression method of FIG. 5A. Such a compression method ofFIG. 5B is particularly advantageous when the internal digital value NAis that which represents the writing pressure value. Specifically, thewriting pressure value has a characteristic that the user becomes moresensitive to an error when the value becomes smaller. According to thecompression method of FIG. 5B, the compression rate of the standarddigital value MS can be made lower when the writing pressure value issmaller (i.e., the internal digital value NA is smaller). Therefore,according to the compression method of FIG. 5B, it becomes possible toreduce the possibility that the user notices an error that possiblyoccurs at the time of transmission of the standard digital value MS.

Referring back to FIG. 4 , the integrated circuit 27 that has acquiredthe standard digital value MS in step S6 sets the acquired standarddigital value MS as the transmission digital value MD (step S7). Inaddition, the integrated circuit 27 restores the internal digital valueNA from the standard digital value MS (step S8). This restoration iscarried out by the same method as the restoration carried out by thesensor device 3.

The integrated circuit 27, when the processing is forwarded to step S9,sets the relative digital value MR that is the relative value expressedwith M bits as the transmission digital value MD (step S9). In addition,the integrated circuit 27 restores the internal digital value NA fromthe relative digital value MR by using the already-supplied internaldigital value NS (step S10). This restoration is also carried out by thesame method as the restoration carried out by the sensor device 3.

The integrated circuit 27 that has carried out step S8 or step S10subsequently sets the restored internal digital value NA in thealready-supplied internal digital value holding circuit 103 (step S11).Then, the integrated circuit 27 transmits the transmission data MF,which is obtained by adding the identification flag F according to thevalue set in the transmission digital value MD to the transmissiondigital value MD (step S12), and returns to step S1 to continue theprocessing.

FIG. 6 and FIG. 7 are diagrams illustrating specific examples of therespective values used in the process of the processing illustrated inFIG. 4 . FIG. 6 illustrates a case in which the standard digital valueMS is set as the transmission digital value MD (i.e., a case in whichstep S6 in FIG. 4 is carried out). FIG. 7 illustrates a case in whichthe relative digital value MR is set as the transmission digital valueMD (i.e., a case in which step S9 in FIG. 4 is carried out).Furthermore, FIG. 6 and FIG. 7 illustrate cases in which the compressionmethod illustrated in FIG. 5A is used as the method for acquiring thestandard digital value MS from the internal digital value NA.

Referring first to FIG. 6 , as the transmission digital value MD in thiscase, the standard digital value MS is set which comprises the M mostsignificant bits of the internal digital value NA. Furthermore, thetransmission data MF is composed of the standard digital value MS andthe identification flag F having the value indicating the standarddigital value MS (the first value, for example, “1”). Thealready-supplied internal digital value NS after the transmission dataMF is transmitted (i.e., what is set in the already-supplied internaldigital value holding circuit 103 in step S11) is the internal digitalvalue NA restored from the standard digital value MS, i.e., the valueobtained by adding N−M “0” bits to the least significant side of thestandard digital value MS.

Referring next to FIG. 7 , as the transmission digital value MD in thiscase, the M-bit relative digital value MR calculated from the internaldigital value NA and the already-supplied internal digital value NS isset. Furthermore, the transmission data MF is composed of the relativedigital value MR and the identification flag F having the valueindicating the relative digital value MR (the second value differentfrom the first value, for example, “0”). The already-supplied internaldigital value NS after the transmission data MF is transmitted (i.e.,what is set in the already-supplied internal digital value holdingcircuit 103 in step S11) is the internal digital value NA restored fromthe relative digital value MR by using the already-supplied internaldigital value NS, i.e., the internal digital value NA itself acquired instep S1.

FIG. 8 is a flowchart illustrating a reception processing of theinternal digital value NA executed by the sensor controller 31. Withreference to this diagram, the reception processing of the internaldigital value NA executed by the sensor controller 31 will be describedin detail below.

First, the sensor controller 31 receives the transmission data MFthrough the sensor 30, for example (step S20). Then, based on theidentification flag F included therein, the sensor controller 31determines whether the transmission digital value MD in the transmissiondata MF is the standard digital value MS or the relative digital valueMR (step S21).

When determining that the transmission digital value MD is the standarddigital value MS in step S21, the sensor controller 31 executesprocessing of restoring the N-bit internal digital value NA from thereceived M-bit transmission digital value MD (=the standard digitalvalue MS) (step S22). The specific content of this processing is asdescribed with reference to FIGS. 5A and 5B.

On the other hand, the sensor controller 31 that has determined that thetransmission digital value MD is the relative digital value MR in stepS21 executes processing of restoring the N-bit internal digital value NAfrom the received M-bit transmission digital value MD (=the relativedigital value MR) by using the value stored in the internal memorypreviously in step S24 to be described later (step S23). This processingis executed as inverse processing of the method used by the pen 2 toacquire the relative value in step S4 in FIG. 4 (for example, theprocessing of adding the relative digital value MR to the value storedin the internal memory).

The sensor controller 31 that has carried out step S22 or step S23subsequently outputs the restored N-bit internal digital value NA to thehost computer 4 (see FIG. 1 ) and stores it in the internal memory (stepS24). Thereafter, the sensor controller 31 returns the processing tostep S20 and waits for reception of the next transmission data MF. Theinternal digital value NA stored in the internal memory in step S24 isused when step S23 is carried out next.

As described above, according to the present embodiment, the N-bitinternal digital value NA can be supplied with the transmission data MFsmaller than N bits (specifically, with M+1 bits). Thus, it becomespossible to alleviate insufficiency of communication resources that canbe used for communication between the pen 2 and the sensor device 3.

Furthermore, according to the present embodiment, the number of bits ofthe standard digital value MS is also set to M, and therefore it becomespossible to carry out transmission of the transmission data MF by usinga fixed-length communication method. In this case, immediately after thestandard digital value MS is received, an error is possibly included inthe internal digital value NA restored in the sensor device 3. However,this error is eliminated by the relative digital value MR which issubsequently transmitted.

Moreover, according to the present embodiment, through acquisition ofthe standard digital value MS by use of the compression methodillustrated in FIG. 5B, it becomes possible to reduce the possibilitythat the user feels or recognizes an error at the time of transmissionof the standard digital value MS.

In addition, according to the present embodiment, the standard digitalvalue MS is transmitted instead of the relative digital value MR in acertain case. Therefore, even when an error occurs between the internaldigital value NA acquired by the pen 2 and the internal digital value NAacquired by the sensor device 3 due to a communication error or thelike, the error can be eliminated after transmission and reception ofthe standard digital value MS. This effect will be described in detailbelow with reference to FIGS. 9A and 9B.

FIG. 9A is a diagram illustrating a temporal change in various digitalvalues acquired in each of the pen 2 and the sensor device 3. In thisdiagram, N=12 and M=7. In the example of this diagram, the standarddigital value MS (a value with hatching) is set as the transmissiondigital value MD at clock times t₁ and t₇ and the relative digital valueMR (a value without hatching) is set as the transmission digital valueMD at clock times t₂ to t₆.

The clock time t₁ is the clock time when supply of the internal digitalvalue NA from the pen 2 to the sensor device 3 has started. At the stagebefore the clock time t₁, the internal digital value NA written last inthe last communication between the pen 2 and the sensor device 3 is heldin the already-supplied internal digital value holding circuit 103. Therelative value between the internal digital value NA thus held and theinternal digital value NA newly acquired is normally a large value like“−200” exemplified in FIG. 9A, for example, and therefore the standarddigital value MS is transmitted also at the clock time t₁. However,after the communication between the pen 2 and the sensor device 3 ends,the integrated circuit 27 may overwrite the held content of thealready-supplied internal digital value holding circuit 103 with apredetermined value. Although the specific value of this predeterminedvalue is not particularly limited, it is preferable to use a value farfrom values that can be normally taken by the internal digital value NA(for example, the maximum value “4095 (=111111111111)”). This canprevent the relative digital value MR from being transmitted first inthe next communication. Furthermore, the reason why the standard digitalvalue MS is transmitted at the clock time t₇ is that the internaldigital value NA “1088 (=010001000000)” corresponds with the value “1088(=010001000000)” obtained by adding N−M “0” bits to the tail end of thestandard digital value MS “34 (=0100010)” obtained from this internaldigital value NA and, hence, the determination result of step S3 in FIG.4 is positive (“YES”).

In FIG. 9A, a communication error occurs at the clock times t₄ and t₅and the transmission data MF does not reach the sensor device 3. As aresult, at the clock times t₄ to t₆, the internal digital value NAacquired by the pen 2 does not correspond with the internal digitalvalue NA restored in the sensor device 3. However, due to thetransmission of the standard digital value MS by the pen 2 at the clocktime t₇, they return to the corresponding state again. As above,according to the present embodiment, the error that occurs due to acommunication error can be eliminated by the standard digital value MS,which is transmitted when the internal digital value NA can be restoredfrom the standard digital value MS without an error.

Next, FIG. 9B is also a diagram illustrating a temporal change invarious digital values acquired in each of the pen 2 and the sensordevice 3. Also in this diagram, N=12 and M=7. The situation up to theclock time t₆ in the example of this diagram is the same as in FIG. 9A.At the clock times t₄ to t₆, the internal digital value NA acquired bythe pen 2 does not correspond with the internal digital value NArestored in the sensor device 3. Thereafter, the internal digital valueNA changes significantly at the clock time t₇. As a result, the relativevalue exceeds the range in which the relative value can be expressedwith M bits (with M=7, −64 to +63) and thus the pen 2 transmits thestandard digital value MS at the clock time t₇. As a result, similarlyto the case of FIG. 9A, the internal digital value NA acquired by thepen 2 corresponds with the internal digital value NA restored in thesensor device 3 again at the clock time t₇. As above, according to thepresent embodiment, the error that occurs due to a communication errorcan be eliminated also by the standard digital value MS, which istransmitted when the relative value cannot be expressed with M−1 bits.When the standard digital value MS is thus transmitted, there is apossibility that the internal digital value NA acquired by the pen 2does not correspond with the internal digital value NA restored in thesensor device 3 and thus an error remains. However, as described above,this error is eliminated by the immediately-subsequent relative digitalvalue MR. In addition, the impact of this error on the perception of ahuman user is limited and therefore this error does not become asignificant program.

FIG. 10 to FIG. 13 are diagrams illustrating a working example of thepresent embodiment. Curves illustrated in the upper portions of FIG. 11to FIG. 13 represent the internal digital value NA (e.g., a writingpressure value) sequentially acquired by the integrated circuit 27 (seeFIG. 3 ) when a user inputs three strokes A1 to A3 illustrated in FIG.10 by using the pen 2. In FIGS. 11-13 , white circle marks representthat the standard digital value MS is set as the transmission digitalvalue MD at the timing and the specific value of the set standarddigital value MS. White triangle marks represent that the relativedigital value MR is set as the transmission digital value MD at thetiming and the specific value of the set relative digital value MR.Moreover, curves illustrated in the lower portions of FIG. 11 to FIG. 13represent the error between the original internal digital value NA andthe internal digital value NA restored from the transmission digitalvalue MD. Examples where N=10 and M=7 are illustrated in FIG. 11 andFIG. 12 , and an example where N=12 and M=7 is illustrated in FIG. 13 .Furthermore, FIG. 12 illustrates an example in which the determinationresult of step S3 illustrated in FIG. 4 is fixed as the negative result(i.e., a case in which, even when the internal digital value NA can berestored from the standard digital value MS without an error,transmission of the standard digital value MS for that reason is notcarried out).

Referring first to FIG. 11 , it is understood that the standard digitalvalue MS is set as the transmission digital value MD at portions inwhich the internal digital value NA changes significantly, at the startand end of each stroke, whereas the relative digital value MR is set asthe transmission digital value MD at portions in which a change in theinternal digital value NA is small, mostly in the middle of each stroke.Furthermore, it is understood that, in the middle of each stroke, thestate in which the error between the original internal digital value NAand the internal digital value NA restored from the transmission digitalvalue MD is 0 continues including the case in which the standard digitalvalue MS is set as the transmission digital value MD. The case in whichthe standard digital value MS is set as the transmission digital valueMD and the error between the original internal digital value NA and theinternal digital value NA restored from the transmission digital valueMD becomes 0 is, in short, the case in which the standard digital valueMS is set as the transmission digital value MD because the determinationresult of step S3 in FIG. 4 is positive. Moreover, it is understood thatthe absolute value of the error between the original internal digitalvalue NA and the internal digital value NA restored from thetransmission digital value MD is up to 4.

From the example of FIG. 11 , it can be said that, according to thepresent embodiment, the internal digital value NA can be transmittedfrom the pen 2 to the sensor device 3 in the state in which the error issufficiently small at least in the case of N=10 and M=7. Therefore, itbecomes possible to apply the present embodiment to the pen system 1 andreduce communication resources used for transmission of the internaldigital value NA. Thus, according to the present embodiment,insufficiency of communication resources that can be used forcommunication between the pen 2 and the sensor device 3 can bealleviated.

Referring next to FIG. 12 , it is understood that a result similar tothat when step S3 is carried out is obtained even when step S3 isskipped. Therefore, in this case, it is not necessarily essential todetermine whether or not the internal digital value NA can be restoredfrom the standard digital value MS without an error and to change theprocessing according to the determination result.

Lastly, referring to FIG. 13 , in the example of this diagram, the casein which the standard digital value MS is set as the transmissiondigital value MD is more frequent compared with FIG. 11 , and theabsolute value of the error between the original internal digital valueNA and the internal digital value NA restored from the transmissiondigital value MD is a large value (at most 15) in a wide range. In thiscase, it is difficult to apply the present embodiment to the pen system1, and insufficiency of communication resource that can be used forcommunication between the pen 2 and the sensor device 3 may not bealleviated by the present embodiment in the case of N=12 and M=7. Afurther technique may be needed to achieve the desired effect also inthe case of N=12 and M=7. In the second and third embodiments to bedescribed below, some examples of such technique will be described.

FIG. 14 is a diagram explaining the principle of the second embodimentof the present disclosure. The present embodiment is different from thefirst embodiment in that a medium-accuracy relative digital value MM isused in addition to the relative digital value MR used also in the firstembodiment, and is the same as the first embodiment in other respects.In the following, the description will be continued with focus on thedifference from the first embodiment.

The integrated circuit 27 according to the present embodiment isconfigured to, in transmitting the N-bit internal digital value NA,transmit the transmission data MF with bits smaller than N bitsincluding the transmission digital value MD that is any of the M-bitstandard digital value MS, the L-bit (L<M) medium-accuracy relativedigital value MM, or the L-bit relative digital value MR, which areillustrated in the diagram, instead of the internal digital value NAitself. An example with L=M−1 is illustrated in FIG. 14 and thedescription will be continued using this example in the following.However, it suffices for L to be an integer smaller than M, and L=M−1does not need to be satisfied.

One identification flag F1 is included in the transmission data MF ifthe transmission digital value MD is the standard digital value MS. Onthe other hand, two identification flags F1 and F2 are included in thetransmission data if the transmission digital value MD is themedium-accuracy relative digital value MM or the relative digital valueMR. The identification flag F1 is one-bit data that becomes a firstvalue (for example, “1”) if the transmission digital value is thestandard digital value MS, and becomes a second value (for example, “0”)different from the first value if the transmission digital value is notthe standard digital value MS. The identification flag F2 is one-bitdata that becomes a third value (for example, “1”) if the transmissiondigital value is the medium-accuracy relative digital value MM, andbecomes a fourth value (for example, “0”) different from the third valueif the transmission digital value is the relative digital value MR.

The relative digital value MR according to the present embodiment iscomposed of the relative value expressed with L bits, when the relativevalue described in the first embodiment is what can be expressed with Lbits. The medium-accuracy relative digital value MM is composed of the Lmost significant bits of the relative value expressed with L+K bits,when the relative value described in the first embodiment is what can beexpressed with L+K bits (1≤K≤N−M). The medium-accuracy relative digitalvalue MM may be obtained by compressing the internal digital value NA bythe same compression method as the compression method illustrated inFIG. 5B.

FIG. 15 is a flowchart illustrating a transmission processing of theinternal digital value NA executed by the integrated circuit 27according to the present embodiment. With reference to FIG. 15 , thetransmission processing of the internal digital value NA executed by theintegrated circuit 27 according to the present embodiment will bedescribed in detail below. The processing flow of FIG. 15 replaces aportion of FIG. 4 .

After acquiring the relative value between the already-supplied internaldigital value NS and the internal digital value NA by carrying out stepS4 of FIG. 4 , the integrated circuit 27 according to the presentembodiment determines whether or not the acquired relative value can beexpressed with L bits (step S30). When determining that the relativevalue cannot be so expressed, the integrated circuit 27 moves theprocessing to step S33. When determining that the relative value can beexpressed, the integrated circuit 27 moves the processing to step S31.

In step S31, the integrated circuit 27 sets the relative digital valueMR, which is the relative value expressed with L bits, as thetransmission digital value MD (step S31) and moves the processing tostep S10 of FIG. 4 .

On the other hand, in step S33, the integrated circuit 27 determineswhether or not the relative value acquired in step S4 can be expressedwith L+K bits (step S33). When determining that the relative valuecannot be so expressed, the integrated circuit 27 moves the processingto step S6 of FIG. 4 . When determining that the relative value can beexpressed, the integrated circuit 27 moves the processing to step S34.

In step S34, the integrated circuit 27 sets the medium-accuracy relativedigital value MM, which is the L most significant bits of the relativevalue expressed with L+K bits, as the transmission digital value MD(step S34). Then, the integrated circuit 27 restores the internaldigital value NA from the medium-accuracy relative digital value MM byusing the already-supplied internal digital value NS (step S35) andthereafter moves the processing to step S11 of FIG. 4 . The restorationprocessing is carried out by the same method as the restoration carriedout by the sensor device 3 in steps S8 and S10 illustrated in FIG. 4 .

FIG. 16 is a flowchart illustrating a reception processing of theinternal digital value NA executed by the sensor controller 31 accordingto the present embodiment. With reference to this diagram, the receptionprocessing of the internal digital value NA executed by the sensorcontroller 31 according to the present embodiment will be described indetail below. The processing flow of FIG. 16 replaces a portion of FIG.8 .

After receiving the transmission data MF by carrying out step S20 ofFIG. 8 , the sensor controller 31 according to the present embodimentdetermines whether or not the transmission digital value MD in thetransmission data MF is the standard digital value MS based on theidentification flag F1 included in the transmission data MF (step S40).

When determining that the transmission digital value MD is the standarddigital value MS in step S40, the sensor controller 31 moves theprocessing to step S22 in FIG. 8 (i.e., the step of restoring theinternal digital value NA from the standard digital value MS). On theother hand, when determining that the transmission digital value MD isnot the standard digital value MS in step S40, the sensor controller 31further determines whether the transmission digital value MD in thetransmission data MF is the relative digital value MR or themedium-accuracy relative digital value MM based on the identificationflag F2 included in the received transmission data MF (step S41).

The sensor controller 31, when determining that the transmission digitalvalue MD is the relative digital value MR in step S41, executesprocessing of restoring the N-bit internal digital value NA from thereceived L-bit transmission digital value MD (=the relative digitalvalue MR) by using the value previously stored in the internal memory instep S24 of FIG. 8 (step S42). This processing is executed as inverseprocessing of the method used by the pen 2 to acquire the relative valuein step S4 of FIG. 4 .

On the other hand, the sensor controller 31, which has determined thatthe transmission digital value MD is the medium-accuracy relativedigital value MM in step S41, executes processing of restoring the N-bitinternal digital value NA from the received L-bit transmission digitalvalue MD (=the medium-accuracy relative digital value MM) by using thevalue previously stored in the internal memory in step S24 of FIG. 8(step S43). This processing is executed by first adding K “0” bits tothe least significant side of the transmission digital value MD toacquire a digital value of L+K bits and executing, on this digitalvalue, inverse processing of the method used by the pen 2 to acquire therelative value in step S4 of FIG. 4 .

The sensor controller 31 that has carried out step S42 or step S43 movesthe processing to step S24 of FIG. 8 (the step of outputting therestored N-bit internal digital value NA and storing it in the internalmemory).

FIG. 17 is a diagram illustrating a working example of the presentembodiment. The meanings of the curve, white circle marks, and whitetriangle marks in the upper portion of this diagram and the curve in thelower portion of this diagram are the same as those in FIG. 11 to FIG.13 . Black square marks illustrated in the upper portion of FIG. 17represent that the medium-accuracy relative digital value MM is set asthe transmission digital value MD at the timing and the specific valueof the set medium-accuracy relative digital value MM. In FIG. 17 , anexample where N=12 and M=8 is illustrated as with FIG. 13 . L=M−1=7 issatisfied.

As is understood from FIG. 17 , in the present working example, themedium-accuracy relative digital value MM is set as the transmissiondigital value MD at places at which a change in the internal digitalvalue NA is at a medium degree. As a result, the range in which theerror (discrepancy) between the original internal digital value NA andthe internal digital value NA restored from the transmission digitalvalue MD becomes large is small compared with the example of FIG. 13 .As a result, in the present embodiment, there are fewer issuesassociated with actually using the pen system 1 as compared with thefirst embodiment. Therefore, according to the present embodiment,insufficiency of communication resources that can be used forcommunication between the pen 2 and the sensor device 3 can bealleviated also in the case where N=12 and M=8.

Although the example in which one kind of medium-accuracy relativedigital value MM is used is described in the present embodiment, pluralkinds of medium-accuracy relative digital value MM may be used. Forexample, an medium-accuracy relative digital value that comprises the Lmost significant bits of a relative value expressed with L+K1 bits(1≤K1≤N−M) and an medium-accuracy relative digital value that comprisesthe L most significant bits of a relative value expressed with L+K2 bits(1≤K2≤N−M and K2>K1) may be used. In this case, the identification flagmay be one to identify whether the number of kinds of medium-accuracyrelative digital value increases or decreases, for example.

Furthermore, the magnitude of the value represented by one bit of themedium-accuracy relative digital value MM (i.e., a value of K) may bechanged adaptively according to the relative value or the amount of achange in the relative value. In this case, the identification flag maybe what represents the change ratio of the magnitude of the valuerepresented by one bit of the medium-accuracy relative digital value MM(i.e., a ratio between K before the change and K after the change).

In the present embodiment, the example is described in which the one-bitidentification flag is added to the standard digital value MS and thetwo-bit identification flag is added to the relative digital value MRand the medium-accuracy relative digital value MM. However, the one-bitidentification flag may be added to one of the relative digital value MRand the medium-accuracy relative digital value MM, and the two-bitidentification flag may be added to the other of the relative digitalvalue MR and the medium-accuracy relative digital value MM, and thestandard digital value MS. This makes it possible to set the number ofbits of one of the relative digital value MR and the medium-accuracyrelative digital value MM to M bits and to set the other of the relativedigital value MR and the medium-accuracy relative digital value MM, andthe standard digital value MS, to L bits. In short, how many bits of theflag are assigned to which type of writing pressure expression (e.g.,the standard digital value MS, the medium-accuracy relative digitalvalue MM, or the relative digital value MR, and so forth) can bearbitrarily set.

FIG. 18 is a flowchart illustrating a transmission processing of theinternal digital value NA executed by the integrated circuit 27according to the third embodiment of the present disclosure. Theprocessing flow of FIG. 18 replaces a portion of FIG. 4 . The presentembodiment is different from the first embodiment in that a relativevalue between a predicted value P of the internal digital value NA andthe internal digital value NA is used, instead of the relative valuebetween the already-supplied internal digital value NS and the internaldigital value NA, and is the same as the first embodiment in otherrespects. In the following, the description will be continued with focuson the difference from the first embodiment.

The already-supplied internal digital value holding circuit 103 of theintegrated circuit 27 according to the present embodiment is configuredto store a defined number of the internal digital values NA(s) (as setin step S11). Furthermore, as illustrated in FIG. 18 , after thenegative determination in step S3, the integrated circuit 27 accordingto the present embodiment executes processing of acquiring the predictedvalue P of the internal digital value NA from the stored defined numberof the internal digital values NA(s) based on a predetermined predictionrule (step S50). This processing can be executed based on aninterpolation curve of the defined number of the internal digital valuesNA(s), for example. As one example, an example based on an interpolationcurve of two (the defined number=2) of the internal digital values NA(s)will be described in detail. First, the interpolation curve of the twoprevious internal digital values NA(s) is obtained. The interpolationcurve in this case is a straight line, and NA(n)=−10n+1080 is obtainedas the interpolation curve if the two previous internal digital valuesNA(s) are “1100” and “1090,” for example. For example, NA(n) mayrepresent the n-th internal digital value NA in a series, and n is anumerical value that becomes −2 for the internal digital value NA beforelast (two times before), −1 for the internal digital value NA of thelast time (one time before), and 0 for the internal digital value NA ofthe present time. By substituting n=0 in the interpolation curve thusobtained, the predicted value P can be obtained as “1080.”

The integrated circuit 27, which has carried out step S50, executesprocessing of acquiring the relative value between the predicted value Pand the internal digital value NA acquired in step S1 instead of step S4of FIG. 4 (step S51). The relative value acquired here is the differencebetween the predicted value P and the internal digital value NA acquiredin step S1, for example. Thereafter, the integrated circuit 27 moves theprocessing to step S5 and executes the processing described withreference to FIG. 4 .

Next, FIG. 19 is a flowchart illustrating a reception processing of theinternal digital value NA executed by the sensor controller 31 accordingto the present embodiment. The processing flow of FIG. 19 replaces aportion of FIG. 8 .

The sensor controller 31 according to the present embodiment isconfigured to store a defined number of the internal digital valuesNA(s) (as stored in step S24) in the internal memory. As illustrated inFIG. 19 , when determining that the transmission digital value MD in thetransmission data MF is the relative digital value MR in step S21, thesensor controller 31 according to the present embodiment executesprocessing of acquiring the predicted value P of the internal digitalvalue NA from the stored determined number of the internal digitalvalues NA(s) based on the predetermined prediction rule (step S60). Thisprocessing is executed by the same method as in step S50 of FIG. 18 .

The sensor controller 31, which has carried out step S60, executes,instead of step S23 of FIG. 8 , processing of restoring the N-bitinternal digital value NA from the received M-bit transmission digitalvalue MD (=the relative digital value MR) by using the predicted value P(step S61). This processing is executed as inverse processing of themethod used by the pen 2 to acquire the relative value in step S51 ofFIG. 8 (for example, the processing of adding the relative digital valueMR to the predicted value P). Thereafter, the sensor controller 31 movesthe processing to step S24 and executes the processing described withreference to FIG. 8 .

FIG. 20 is a diagram illustrating a working example of the presentembodiment. The meanings of the curve, white circle marks, and whitetriangle marks in the upper portion of this diagram and the curve in thelower portion of this diagram are the same as those in FIG. 11 to FIG.13 and FIG. 17 . In FIG. 20 , an example in which N=12 and M=7 isillustrated as with FIG. 13 and FIG. 17 .

As is understood from FIG. 20 , in the present working example, therange in which the error (difference) between the original internaldigital value NA and the internal digital value NA restored from thetransmission digital value MD becomes large is small compared with theexamples of FIG. 13 and FIG. 17 . As a result, in the presentembodiment, there are fewer issues associated with actually using thepen system 1 than in the second embodiment. Therefore, also by thepresent embodiment, insufficiency of communication resources that can beused for communication between the pen 2 and the sensor device 3 can bealleviated also in the case where N=12 and M=7.

FIG. 21 is a diagram illustrating a temporal change in various digitalvalues acquired in each of the pen 2 and the sensor device 3 accordingto the fourth embodiment of the present disclosure. As illustrated inthis diagram, the present embodiment is different from the firstembodiment in that the reference value Ref is supplied from the sensordevice 3 to the pen 2, and the already-supplied internal digital valueNS is updated based on this reference value Ref, and is the same as thefirst embodiment in other respects. In the following, the descriptionwill be continued with focus on the difference from the firstembodiment.

As illustrated in FIG. 21 , the sensor controller 31 according to thepresent embodiment is configured to employ the internal digital value NAstored in the internal memory (a value stored in step S24) as thereference value Ref, and to transmit the reference value Ref toward thepen 2 via the uplink signal US at an arbitrary timing. For example, thearbitrary timing may be immediately after detection of the pen 2 by thesensor controller 31 or may be a timing after the elapse of apredetermined time period from the last reception of the transmissiondata MF from the sensor controller 31. Alternatively, the arbitrarytiming may be a timing decided based on a random number, or may be atiming that periodically occurs, or may be a combination of two or moreof these timings. After transmitting the reference value Ref, the sensorcontroller 31 skips step S24 until transmitting the next reference valueRef or until receiving the standard digital value MS. As a result, thereference value Ref continues to be stored in the internal memory of thesensor controller 31, and processing of restoring the N-bit internaldigital value NA from the received transmission digital value MD of M−1bits (=the relative digital value MR) by using the reference value Refis executed in step S23 of FIG. 8 .

FIG. 22 is a schematic block diagram illustrating functional blocks ofthe integrated circuit 27 according to the present embodiment. Asillustrated in this diagram, the integrated circuit 27 according to thepresent embodiment is configured to functionally include a receptioncircuit 104, additionally. The reception circuit 104 is a functionalunit that receives the uplink signal US through the antenna 22 andextracts the reference value Ref from the received uplink signal US toset the reference value Ref in the already-supplied internal digitalvalue holding circuit 103.

The integrated circuit 27 according to the present embodiment carriesout operation of supplying the internal digital value NA to the sensordevice 3 according to the value held in the already-supplied internaldigital value holding circuit 103. Specifically, until the referencevalue Ref is set in the already-supplied internal digital value holdingcircuit 103, the integrated circuit 27 executes the same processing asthe first embodiment as illustrated in FIG. 21 . However, once thereference value Ref is set in the already-supplied internal digitalvalue holding circuit 103, afterward, step S11 of FIG. 4 is skipped aslong as the processing is executed through step S10 of FIG. 4 . As aresult, while the relative digital value MR continues to be set as thetransmission digital value MD, the already-supplied internal digitalvalue NS continues to be the reference value Ref and, in step S4 of FIG.4 , the relative value between the reference value Ref and the internaldigital value NA acquired in step S1 is acquired.

Due to the execution of the above processing by the pen 2 and the sensordevice 3, generation of the relative value and restoration of theinternal digital value NA are carried out based on the reference valueRef after the reference value Ref is transferred as illustrated in FIG.21 . This processing is particularly effective when a communicationerror has occurred as in the example illustrated in FIG. 21 .Specifically, even when an error (discrepancy) occurs between theinternal digital value NA acquired by the pen 2 and the internal digitalvalue NA acquired by the sensor device 3 due to a communication error,the error (discrepancy) can be eliminated after transmission andreception of the reference value Ref.

As described above, according to the present embodiment, even when anerror (discrepancy) occurs between the digital value acquired by the penand the digital value acquired by the sensor device due to acommunication error or the like, the error can be eliminated aftertransmission and reception of the reference value.

In the present embodiment, the example is described in which, once thereference value Ref is set in the already-supplied internal digitalvalue holding circuit 103, afterward step S11 of FIG. 4 is skipped aslong as the processing of the integrated circuit 27 is executed throughstep S10 of FIG. 4 . However, the skipping of step S11 may be limited toone time of skipping immediately after the reference value Ref is set inthe already-supplied internal digital value holding circuit 103. In thiscase, at the clock time t₆ in FIG. 21 , for example, 1030 is set as thealready-supplied internal digital value NS after transmission. In thiscase also, the same effect as the present embodiment can be achieved.

FIG. 23 is a flowchart illustrating processing executed by theintegrated circuit 27 according to a fifth embodiment of the presentdisclosure. The present embodiment is different from the firstembodiment in that the integrated circuit 27 can operate in twooperation modes, and the sensor device 3 can switch the operation modeof the integrated circuit 27, and is the same as the first embodiment inother respects. In the following, the description will be continued withfocus on the difference from the first embodiment.

The integrated circuit 27 according to the present embodiment isconfigured to operate in either a relative digital value use mode, inwhich operation is carried out as in FIG. 4 , and a constant standarddigital value use mode, in which the steps S3 to S5 of FIG. 4 areskipped and the processing of step S6 and the subsequent steps is alwaysexecuted after step S1. Switching between them is carried out by using acommand included in the uplink signal US from the sensor device 3.

The operation of the integrated circuit 27 will be described. Asillustrated in FIG. 23 , first the integrated circuit 27 receives theuplink signal US (step S70). Then, the integrated circuit 27 determineswhether or not a command indicating the operation mode is includedtherein (step S71). If the command is not included, the integratedcircuit 27 keeps the current operation mode and returns the processingto step S70. If the command is included, the integrated circuit 27further determines which of the relative digital value use mode or theconstant standard digital value use mode is indicated. If the relativedigital value use mode is indicated, the integrated circuit 27 entersthe relative digital value use mode (step S72). If the constant standarddigital value use mode is indicated, the integrated circuit 27 entersthe constant standard digital value use mode (step S73). Thereafter, theintegrated circuit 27 returns the processing to step S70.

According to the present embodiment, the pen 2 can send the standarddigital value MS according to a command from the sensor device 3 whenthe sensor device 3 needs the standard digital value MS. Therefore, forexample, when an error occurs between the internal digital value NAacquired by the pen 2 and the internal digital value NA acquired by thesensor device 3 due to the occurrence of a communication error, theerror can be immediately eliminated.

Although preferred embodiments of the present disclosure are describedabove, it is obvious that the present disclosure is not limited to suchembodiments and the present disclosure can be implemented in variousmodes without departing from the scope of the present disclosure.

For example, in the above-described respective embodiments, the examplesare described in which the internal digital value acquisition circuit100 converts the state of the user operation tool 25 (including thewriting pressure detector 23) to the N-bit internal digital value.However, the internal digital value acquisition circuit 100 may acquirethe N-bit internal digital value from a factor or element other than thestate of the user operation tool. For example, data transmitted from thepen 2 to implement setting of the sensor device 3 or the host computer 4may be acquired as the N-bit internal digital value. This data can besupplied also based on M-bit transmission data (M<N). Thus, it becomespossible to further alleviate insufficiency of communication resourcesthat can be used for communication between the pen 2 and the sensordevice 3.

In the above-described respective embodiments, determination of whetheror not to transmit the standard digital value MS is carried out on theside of the pen 2. However, this determination may be carried out alsoin the sensor controller 31, and the sensor controller 31 may cause theelectronic pen 2 to transmit the standard digital value MS by using acommand transmitted in the uplink signal US when the sensor controller31 determines to cause the pen 2 to transmit the standard digital valueMS. In this case, it is preferable for the sensor controller 31 todetermine to cause the pen 2 to transmit the standard digital value MSif the standard digital value MS has never been received after detectionof the pen 2, or when the standard digital value MS has not beenreceived over a predetermined time, or the like. Furthermore, aftercausing the pen 2 to transmit the standard digital value MS, the sensorcontroller 31 may cause the transmission of the standard digital valueMS to continue a predetermined number of times. This continuoustransmission may be implemented through transmission of a command fromthe sensor controller 31 in every transmission, or may be implemented byconfiguring the pen 2 to autonomously transmit the standard digitalvalue MS a predetermined number of times after having received a commandrequesting the transmission of the standard digital value MS.

DESCRIPTION OF REFERENCE SYMBOLS

1 Pen system

2 Pen

3 Sensor device

3 t Touch surface

4 Host computer

20 Core body

21 Pen tip

22 Antenna

23 Writing pressure detector

24 Wheel user operation tool

25 User operation tool

26 Power supply

27 Integrated circuit

30 Sensor

31 Sensor controller

100 Internal digital value acquisition circuit

101 Transmission digital value acquisition circuit

102 Transmission circuit

103 Already-supplied internal digital value holding circuit

104 Reception circuit

A1 to A3 Stroke

DS Downlink signal

F, F1, F2 Identification flag

MD Transmission digital value

MF Transmission data

MM Medium-accuracy relative digital value

MR Relative digital value

MS Standard digital value

NA Internal digital value

OPS State

P Predicted value

Ref Reference value

US Uplink signal

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A pen configured to supply an N-bitinternal digital value to a sensor device, the pen comprising: a writingpressure detector that detects a force applied to a pen tip, an antenna,and an integrated circuit that is coupled to the writing pressuredetector and the antenna and that acquires a series of the internaldigital values based on a state of the writing pressure detector,wherein the series of the internal digital values include a firstinternal digital value and a second internal digital value acquiredsubsequently to the first internal digital value, the integrated circuitsupplies the first internal digital value to the sensor device bytransmitting, from the antenna, first transmission data including afirst standard digital value corresponding to the first internal digitalvalue, and the integrated circuit supplies the second internal digitalvalue to the sensor device by transmitting, from the antenna, secondtransmission data that is smaller than N bits and includes an M-bitrelative digital value (M<N) corresponding to a relative value betweenthe first internal digital value obtained by restoration from the firststandard digital value and the second internal digital value.
 2. The penaccording to claim 1, wherein the integrated circuit includes analready-supplied internal digital value holding circuit that holds thefirst internal digital value restored from the first standard digitalvalue, and the relative value is a relative value between the secondinternal digital value and the first internal digital value held in thealready-supplied internal digital value holding circuit.
 3. The penaccording to claim 2, wherein the relative value is a difference betweenthe second internal digital value and the first internal digital valueheld in the already-supplied internal digital value holding circuit. 4.The pen according to claim 1, wherein the integrated circuit determines,based on the relative value, which of a second standard digital valuecorresponding to the second internal digital value, or the relativedigital value, is to be set in the second transmission data.
 5. The penaccording to claim 4, wherein the integrated circuit determines to setthe relative digital value in the second transmission data when therelative value is a numerical value that can be expressed with M bits,and determines to set the second standard digital value in the secondtransmission data when the relative value is a numerical value thatcannot be expressed with M bits.
 6. The pen according to claim 4,wherein the second standard digital value is an M-bit digital valueobtained by compressing the second internal digital value.
 7. The penaccording to claim 6, wherein the integrated circuit determines to setthe second standard digital value corresponding to the second internaldigital value in the second transmission data irrespective of therelative value when the second internal digital value is allowed to berestored from the second standard digital value without an error.
 8. Thepen according to claim 1, wherein the integrated circuit determines,based on the relative value, which of the second standard digital valuecorresponding to the second internal digital value, the relative digitalvalue that is the relative value expressed with L bits (L<M), or anmedium-accuracy relative digital value that comprises L most significantbits of the relative value expressed with L+K bits (1≤K≤N−M) is to beset in the second transmission data.
 9. The pen according to claim 8,wherein the integrated circuit determines to set the relative digitalvalue in the second transmission data when the relative value is anumerical value allowed to be expressed with L bits, determines to setthe medium-accuracy relative digital value in the second transmissiondata when the relative value is a numerical value that is not allowed tobe expressed with L bits but allowed to be expressed with L+K bits, anddetermines to set the second standard digital value in the secondtransmission data when the relative value is a numerical value that isnot allowed to be expressed with L+K bits.
 10. The pen according toclaim 9, wherein when including the second standard digital value, thesecond transmission data further includes a first identification flagindicating a first value, when including the medium-accuracy relativedigital value, the second transmission data further includes the firstidentification flag indicating a second value different from the firstvalue and a second identification flag indicating a third value, andwhen including the relative digital value, the second transmission datafurther includes the first identification flag indicating the secondvalue and the second identification flag indicating a fourth valuedifferent from the third value.
 11. The pen according to claim 1,wherein the integrated circuit includes an already-supplied internaldigital value holding circuit that holds a reference value correspondingto the internal digital value that has been already supplied when thereference value is received from the sensor device, and the integratedcircuit carries out operation of supplying the internal digital value tothe sensor device according to a value held in the already-suppliedinternal digital value holding circuit.
 12. The pen according to claim11, wherein the integrated circuit acquires the relative value based onthe second internal digital value and the reference value held in thealready-supplied internal digital value holding circuit.
 13. The penaccording to claim 1, wherein the integrated circuit is configured to becapable of acquiring a predicted value of the internal digital valuebased on one or more of the internal digital values that have beenalready supplied to the sensor device, and the integrated circuitacquires the relative value based on the second internal digital valueand the predicted value.
 14. A pen configured to supply an N-bitinternal digital value to a sensor device, the pen comprising: a useroperation tool, an antenna, and an integrated circuit that is coupled tothe user operation tool and the antenna and that acquires a series ofthe internal digital values based on the user operation tool, whereinthe integrated circuit receives a reference value corresponding to theinternal digital value that has been already supplied from the sensordevice and supplies a first internal digital value included in theseries of the internal digital values to the sensor device bytransmitting, from the antenna, transmission data that is smaller than Nbits and includes an M-bit relative digital value (M<N) corresponding toa relative value between the first internal digital value and thereference value.
 15. The pen according to claim 14, wherein thereference value is the internal digital value restored by the sensordevice from the transmission data.
 16. A pen system that includes a penand a device and outputs an N-bit internal digital value, the pencomprising: a writing pressure detector that detects a force applied toa pen tip, an antenna, and an integrated circuit that is coupled to thewriting pressure detector and the antenna and that acquires a series ofthe internal digital values based on a state of the writing pressuredetector, wherein the integrated circuit supplies a first internaldigital value included in the series of the internal digital values tothe sensor device by transmitting, from the antenna, first transmissiondata including a standard digital value obtained by compressing thefirst internal digital value using a compression method, in which aquantization step becomes smaller when a value of the internal digitalvalue is smaller, and the device is configured to restore the firstinternal digital value from the first transmission data and to outputthe first internal digital value.
 17. The pen system according to claim16, wherein the compression method includes converting a discrete valueexpressed with a relatively-large number of bits to a discrete valueexpressed with a relatively-small number of bits.
 18. The pen systemaccording to claim 16, wherein the series of the internal digital valuesinclude a second internal digital value acquired subsequently to thefirst internal digital value, and after transmitting the firsttransmission data from the antenna, the integrated circuit supplies thesecond internal digital value to the sensor device by transmitting, fromthe antenna, second transmission data that is smaller than N bits andincludes an M-bit relative digital value (M<N) corresponding to arelative value between the second internal digital value and the firstinternal digital value obtained by restoration from the standard digitalvalue.
 19. A sensor device that receives supply of a series of internaldigital values each composed of N bits from a pen configured to acquirethe series of internal digital values based on a force applied to a pentip, wherein the series of internal digital values include a firstinternal digital value and a second internal digital value acquiredsubsequently to the first internal digital value, when receiving firsttransmission data including a first standard digital value correspondingto the first internal digital value from the pen, the sensor devicerestores the first internal digital value from the first transmissiondata and stores the first internal digital value in an internal memory,and when receiving, from the pen, second transmission data that issmaller than N bits and includes an M-bit relative digital value (M<N)corresponding to a relative value between the first internal digitalvalue obtained by restoration from the first standard digital value andthe second internal digital value, the sensor device restores the secondinternal digital value from the second transmission data by using avalue stored in the internal memory.
 20. A sensor device that receivessupply of a series of internal digital values each composed of N bitsfrom a pen configured to acquire the series of internal digital valuesbased on a force applied to a pen tip, wherein the sensor devicetransmits a reference value to the pen, and when receiving, from thepen, transmission data that is smaller than N bits and includes an M-bitrelative digital value (M<N) corresponding to a relative value between afirst internal digital value included in the series of internal digitalvalues and the reference value, the sensor device restores the firstinternal digital value from the transmission data by using the referencevalue.